Go Basics

Go Arrays

A fixed number of values of one type, and why assigning an array copies it.

Beginner
2 min read
1 runnable example

What you'll learn

[5]int and [...]int
Arrays are values
Arrays of arrays

Run code →

var scores [5]int

720

644

Items you do not set keep the zero value.

Fixed size, copied on assignment

An array holds a fixed number of values of one type, and its length is part of its type. Arrays are less common than slices in Go, but slices are built on top of them.

[5]int starts with five zeros. [...] lets the compiler count the items. Assigning an array copies every item, so changing copyOfPrimes leaves primes alone. An array of arrays makes a grid.

Key points

The length is part of the type.
Assigning an array copies every item.
Slices are built on arrays.

Runnable Go example

Run code →

main.go

package main

import "fmt"

func main() {
	var scores [5]int // fixed size, zero values
	scores[0] = 72
	scores[4] = 64
	fmt.Println(scores, len(scores))

	primes := [...]int{2, 3, 5, 7}
	copyOfPrimes := primes // arrays are values: this copies all items
	copyOfPrimes[0] = 99
	fmt.Println(primes, copyOfPrimes)

	grid := [2][3]int{{1, 2, 3}, {4, 5, 6}}
	fmt.Println(grid[1][2], grid)
}

Get a Run button for this example Result of running the code

[72 0 0 0 64] 5
[2 3 5 7] [99 3 5 7]
6 [[1 2 3] [4 5 6]]

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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